Antibacterial and Antibiofilm Properties of the Crude Ethanolic, Methanolic and Aqueous Bark and Seed Extracts of Citrullus lanatus Fruit

Abstract

Medicinal plants represent rich sources of potential antimicrobial agents. Studies on antibacterial and biofilm inhibitory properties of the ethanolic, methanolic and aqueous bark and seed extracts of Citrullus lanatus (C. lanatus) fruit was carried out. The bark and seed of C. lanatus were obtained from Karu market, Abuja and extracted separately with ethanol, methanol and water by cold maceration method. The antibacterial activities of the extracts were evaluated using agar well diffusion method against clinical isolates of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Salmonella typhi. The Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the extracts were determined using agar dilution method. Phytochemical screening of the extracts was also carried out using the standard method. The biofilm inhibitory activity of the extracts was evaluated using micro titer plate method. The best activity was against S. aureus and E. coli with zone of inhibition range of 9.00-22.00 mm (S. aureus) and 8.00-20.00 mm (E. coli). The order of activity of the extracts was: methanolic bark > ethanolic bark = aqueous bark > methanolic seed > ethanolic seed > aqueous seed. The MICs of the extracts of both bark and seed are within the range of 6.25-50.00 mg/ml, and the MBCs ranged from 12.50-50.00 mg/ml. Phytochemicals common to all extracts were flavonoids and phenolics; tannins and saponins were detected only in the methanolic and ethanolic bark and seed extracts; alkaloids and steroids were also found only in aqueous bark and seed extracts. Methanolic, ethanolic and aqueous bark and seed extracts at 12.50-50.00% MBCs inhibited biofilm production by the test organism in the range 4.30-95.30%. The crude methanolic bark and seed extracts were more active on the test isolates than the ethanolic and aqueous extracts. The presence of flavonoids and phenolics in all the crude extract may be evidence that they are responsible for the antibacterial activity. In addition, all the crude had antibiofilm activity. Further in vitro and in vivo studies on antibacterial activity, biofilm inhibition and dissolution as well as pharmacological effects of fractions and pure compounds of bark and seed extracts of C. lanatus should be carried out.